Public Health Statement for Dichlorobenzenes
CAS#: 1,2-Dichlorobenzene 95-50-1; 1,3-Dichlorobenzene 541-73-1; 1,4-Dichlorobenzene 106-46-7
PDF Versionpdf icon[199 KB]
This Public Health Statement is the summary chapter from the Toxicological Profile for Dichlorobenzenes. It is one in a series of Public Health Statements about hazardous substances and their health effects. A shorter version, the ToxFAQs™, is also available. This information is important because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present. For more information, call the ATSDR Information Center at 1-888-422-8737.
This public health statement tells you about dichlorobenzenes (DCBs) and the effects of
exposure to them.
The Environmental Protection Agency (EPA)
identifies the most serious hazardous waste sites in
the nation. These sites are then placed on the
National Priorities List (NPL) and are targeted for
long-term federal clean-up activities. 1,2-, 1,3-, and
1,4-Dichlorobenzene have been identified in at least
281, 175, and 330, respectively, of the 1,662 current
or former NPL sites. Although the total number of
NPL sites evaluated for these substances is not
known, the possibility exists that the number of
sites at which dichlorobenzenes are found may
increase in the future as more sites are evaluated.
This information is important because these sites
may be sources of exposure and exposure to these
substances may harm you.
When a substance is released either from a large
area, such as an industrial plant, or from a container,
such as a drum or bottle, it enters the environment.
Such a release does not always lead to exposure.
You can be exposed to a substance only when you
come in contact with it. You may be exposed by
breathing, eating, or drinking the substance, or by
If you are exposed to dichlorobenzenes, many
factors will determine whether you will be harmed.
These factors include the dose (how much), the
duration (how long), and how you come in contact
with them. You must also consider any other
chemicals you are exposed to and your age, sex,
diet, family traits, lifestyle, and state of health.
What are dichlorobenzenes?
Each of the three types of DCBs (i.e., 1,2-DCB,
1,3-DCB, and 1,4-DCB) contains two chlorine
atoms connected to one benzene molecule.
1,2-DCB is a colorless to pale yellow liquid used to
make herbicides. 1,3-DCB is a colorless liquid used
to make herbicides, insecticides, medicine, and
dyes. 1,4-DCB, the most important of the three
chemicals, is a colorless to white solid. It smells
like mothballs and it is one of two chemicals
commonly used to make mothballs. 1,4-DCB also
is used to make deodorant blocks used in garbage
cans and restrooms, and to help control odors in
animal-holding facilities. 1,4-DCB has been used
as an insecticide on fruit and as an agent to control
mold and mildew growth on tobacco seeds, leather,
and some fabrics. Recently, using 1,4-DCB to
make resins has become very important.
When a package of 1,4-DCB is opened, it
‘sublimates', that is, it slowly changes from a solid
into a vapor, and enters the atmosphere. The vapor acts as a deodorizer and insect killer. Most of the
1,2-, 1,3-, and 1,4-DCB released into the
environment is present as a vapor. DCBs can burn,
but they do not burn easily. Most people begin to
smell 1,4-DCB when it is in the air at a
concentration of 0.18 parts per million (ppm) and
0.011 ppm in water.
DCBs do not occur naturally; chemical companies
produce them to make products for home use and
other chemicals such as herbicides and plastics.
What happens to dichlorobenzenes when they
enter the environment?
Most of the 1,4-DCB enters the environment when
it is used in mothballs and in toilet-deodorizer
blocks. Some 1,4-DCB is released to the air by
factories that make or use it, and only a little is
released to soil and water. Very little 1,4-DCB
enters the environment from hazardous waste sites.
Some 1,2- and 1,3-DCBs are released into the
environment when used to make herbicides and
when people use products that contain these
chemicals. Companies that make 1,4-DCB also
make unwanted amounts of 1,2-DCB during the
process. 1,2-DCB is released to the environment
when companies dispose of these unwanted
Because DCBs do not dissolve easily in water, the
small amounts that enter water quickly evaporate
into the air. If they are released to groundwater,
they may be transported through the ground to
surface water. Sometimes, DCBs bind to soil and
sediment. DCBs in soil usually are not easily broken down by soil organisms. Evidence suggests
that plants and fish absorb DCBs. 1,4-DCB has
been detected at concentrations of up to 470 parts
per billion (ppb) in fish.
How might I be exposed to dichlorobenzenes?
Humans are exposed to 1,4-DCB mainly by
breathing vapors from 1,4-DCB products used in
the home, such as mothballs and toilet-deodorizer
blocks. Reported levels of 1,4-DCB in some homes
and public restrooms have ranged from 0.291 to
272 parts of 1,4-DCB per billion parts (ppb) of air.
1,2- and 1,3-DCB are not found frequently in the air
of homes and buildings because, unlike 1,4-DCB,
these chemicals are not used in household products.
Outdoor levels of 1,4-DCB range from 0.01 to
1 ppb and are much lower than levels in homes and
buildings. Levels in the air around hazardous waste
sites are low and range from 0.01 to 4.2 ppb.
Outdoor air levels generally range from 0.01 to
0.1 ppb for 1,2-DCB and from 0.001 to 0.1 ppb for
DCBs have been found in samples of drinking water
from surface water sources. 1,4-DCB was found in
13% of surface water samples collected during a
national survey. These samples contained about
0.008–154 ppb of 1,4-DCB. DCBs also have been
found in drinking water from wells but at low
concentrations. DCBs are found only infrequently
in soil, but they have been detected in soil around
hazardous waste sites in the United States.
DCBs have been detected in beef, pork, chicken,
eggs, baked goods, soft drinks, butter, peanut butter, fruits, vegetables, and fish. However, the levels of
DCBs in foods are generally low.
The average daily adult intake of 1,4-DCB is about
35 micrograms (µg), which comes mainly from
breathing 1,4-DCB vapors released from products
in homes and businesses. The average daily adult
respiratory exposure of the other DCBs is about
1.8 µg for 1,2-DCB and about 0.8 µg for 1,3-DCB.
Individuals can be occupationally exposed to DCBs
in workplace air at much higher levels than the
general public is exposed. Levels measured in the
air of factories that make or process 1,4-DCB
products have ranged from 5.6 to 748 ppm of air.
In addition, people who live or work near industrial
facilities or hazardous waste sites that have high
levels of DCBs may have greater exposure to these
compounds due to emissions from the facilities and
waste sites. People who work or live in buildings
where air fresheners, toilet block deodorants, or
moth balls containing 1,4-DCB are used also are
expected to have a higher exposure to this
compound, which could occur from skin contact as
well as by breathing.
How can dichlorobenzenes enter and leave my
The main way DCBs enter your body is through the
lungs when you breathe in DCB vapors released in
the workplace or in the home from use of products
that contain it. When you breathe in these
chemicals for a few hours, it is likely that some of
the DCBs that have entered your body will get into
DCBs also can get into your body if you drink water
or eat certain foods that contain them, such as meat,
chicken, eggs, or fish. Most of the DCBs that enter
your body from food and water will get into your
bloodstream. It is not likely that DCBs will enter
your body through the skin if you touch products
that contain them.
1,4-DCB used in the home could be accidentally
swallowed, especially by young children. This
possibility exists because household products that
contain 1,4-DCB, particularly some kinds of
mothballs and deodorant blocks, might be freely
available in closets or bathrooms.
Most of the DCB that enters your body (perhaps
more than 95%) leaves through the urine in less
than a week. Small amounts (perhaps 1–2%) leave
your body in the feces and in the air you breathe
out. Tiny amounts remain in your fat and might
stay there for a long time.
Most of the DCBs that enter your body are changed
into other chemicals, mainly dichlorophenols. It is
not known if these breakdown products are more or
less harmful than the DCBs themselves.
How can dichlorobenzenes affect my
Scientists use many tests to protect the public from
harmful effects of toxic chemicals and to find ways
for treating persons who have been harmed.
One way to learn whether a chemical will harm
people is to determine how the body absorbs, uses,
and releases the chemical. For some chemicals, animal testing may be necessary. Animal testing
may also help identify health effects such as cancer
or birth defects. Without laboratory animals,
scientists would lose a basic method for getting
information needed to make wise decisions that
protect public health. Scientists have the
responsibility to treat research animals with care
and compassion. Scientists must comply with strict
animal care guidelines because laws today protect
the welfare of research animals.
Most of the information on health effects of DCBs
is from studies of 1,2- and 1,4-DCB. Very little is
known about the health effects of 1,3-DCB,
especially in humans, but they are likely to be
similar to those of the other DCBs.
Inhaling the vapor or dusts of 1,2-DCB and
1,4-DCB at very high concentrations could be very
irritating to your eyes and nose and cause burning
and tearing of the eyes, coughing, difficult
breathing, and an upset stomach. These
concentrations could occur in workplaces, but are
much higher than you would be exposed to in the
home. 1,4-DCB is the only DCB that is commonly
used in household products (mainly mothballs and
toilet-deodorizer blocks). Scientists have no clear
evidence that the moderate use of common
household products containing 1,4 DCB will cause
any problems to your health. A recent study reports
limited evidence suggesting that inhalation
exposure to 1,4-DCB may result in decreases in
lung function. Some people reported health
problems, such as dizziness, headaches, and liver
problems, from very high levels of 1,4-DCB in the
home. However, these people used very high
amounts of 1,4-DCB products and continued to use
the products for months or even years, even though they felt ill. People who ate 1,4-DCB products
regularly for long periods (months to years) because
of its sweet taste developed skin blotches and
problems with red blood cells, such as anemia (ironpoor
blood). Little information is available about
the effects of skin contact with DCBs. 1,4-DCB
might cause a burning feeling in your skin if you
hold mothballs or toilet-deodorizer blocks against
your skin for a long time.
Breathing or eating any of the DCBs caused
harmful effects in the liver of laboratory animals.
Animal studies also found that 1,2-DCB and
1,4-DCB caused effects in the kidneys and blood,
and that 1,3-DCB caused thyroid and pituitary
effects. There is no clear evidence that 1,2-DCB
and 1,4-DCB impair reproduction or fetal
development in animals at levels below those that
also cause serious health effects in the mother,
although there is an indication that 1,4-DCB can
affect development of the nervous system after
Lifetime exposure to 1,4-DCB by breathing or
eating induced liver cancer in mice. 1,2-DCB was
not carcinogenic in laboratory animals, and
1,3-DCB has not been tested for its potential to
cause cancer. The animal studies suggest that
1,4-DCB could play a role in the development of
cancer in humans, but we do not definitely know
this. The U.S. Department of Health and Human
Services (DHHS) has determined that 1,4-DCB
might be a human carcinogen. The International
Agency for Research on Cancer (IARC) determined
that 1,4-DCB is possibly carcinogenic to humans.
Both IARC and the EPA concluded that 1,2-DCB
and 1,3-DCB are not classifiable as to human
How can dichlorobenzenes affect
This section discusses potential health effects in
humans from exposures during the period from
conception to maturity at 18 years of age.
Children are exposed to DCBs in many of the same
ways adults are. It is possible that mothballs and
toilet bowl deodorant blocks containing 1,4-DCB
could be played with or accidentally swallowed,
especially by young children. Because children
tend to be curious about unknown powders and
liquids, and because these products might be easily
accessible in cabinets, closets, or bathrooms,
children could be at a higher risk of exposure to
1,4-DCB than adults.
Children who are exposed to DCBs are likely to
exhibit the same effects as adults, although this is
not known for certain. Thus, all health problems of
DCBs observed in adults are of potential concern in
Children can also be exposed to DCBs prenatally,
because all three isomers have been detected in
placenta samples, as well as through breast feeding.
There is no reliable evidence suggesting that DCBs
cause birth defects, although animal data raise
concern for effects of 1,4-DCB on postnatal
development of the nervous system.
How can families reduce the risk of
exposure to dichlorobenzenes?
If your doctor finds that you have been exposed to
substantial amounts of DCBs, ask whether your
children might also have been exposed. Your
doctor might need to ask your state health
department to investigate.
You and your children could be exposed to
1,4-DCB in your home if you use consumer
products that contain 1,4-DCB, such as some toilet
bowl cleaners and mothballs. Exposure of children
to 1,4-DCB can be minimized by discouraging them
from playing with, swallowing, or having skin
contact with treated products. These items should
be stored out of reach of young children and kept in
their original containers to prevent accidental
poisonings. Keep your Poison Control Center's
number by the phone.
Is there a medical test to determine
whether I have been exposed to dichlorobenzenes?
Several tests can be used to show if you have been
exposed to DCBs. The most commonly used tests
measure their dichlorophenol breakdown products
in urine and blood. These tests require special
equipment that is not routinely available in a
doctor's office, but they can be performed in a
The presence of the dichlorophenol breakdown
products in the urine indicates a person has been
exposed to DCBs within the previous day or two.
For example, detection of 2,5-dichlorophenol in
urine is commonly used to determine worker
exposure to 1,4-DCB in industrial settings. Another
test measures levels of DCBs in your blood, but this
is used less often. Neither of these tests can be used
to show how high the level of DCB exposure was or
to predict whether harmful health effects will
What recommendations has the federal
government made to protect human health?
The federal government develops regulations and
recommendations to protect public health.
Regulations can be enforced by law. The EPA, the
Occupational Safety and Health Administration
(OSHA), and the Food and Drug Administration
(FDA) are some federal agencies that develop
regulations for toxic substances. Recommendations
provide valuable guidelines to protect public health,
but cannot be enforced by law. The Agency for
Toxic Substances and Disease Registry (ATSDR)
and the National Institute for Occupational Safety
and Health (NIOSH) are two federal organizations
that develop recommendations for toxic substances.
Regulations and recommendations can be expressed
as "not-to-exceed" levels, that is, levels of a toxic
substance in air, water, soil, or food that do not
exceed a critical value that is usually based on
levels that affect animals; they are then adjusted to
levels that will help protect humans. Sometimes
these not-to-exceed levels differ among federal
organizations because they used different exposure
times (an 8-hour workday or a 24-hour day),
different animal studies, or other factors.
Recommendations and regulations are also updated
periodically as more information becomes available.
For the most current information, check with the
federal agency or organization that provides it.
Some regulations and recommendations for
dichlorobenzenes include the following:
The federal government has taken a number of steps
to protect people from excessive exposure to DCBs.
EPA has listed 1,2-, 1,3-, and 1,4-DCB as
hazardous wastes and subjects them to hazardous
waste regulations. EPA has set maximum levels of
600 micrograms (µg) of 1,2-DCB and 75 µg of
1,4-DCB per liter of drinking water. 1,4-DCB is a
pesticide registered with EPA, and its
manufacturers must provide certain kinds of
information to EPA for it to be registered for use as
a pesticide. OSHA has set maximum levels of
50 ppm for 1,2-DCB and 75 ppm for 1,4-DCB in
workplace air for an 8-hour day, 40-hour
Agency for Toxic Substances and Disease Registry (ATSDR). 2006. Toxicological profile for Dichlorobenzenes. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.
Where can I get more information?
If you have questions or concerns, please contact your community or state health or environmental quality department or:
For more information, contact:
Agency for Toxic Substances and Disease Registry
Division of Toxicology and Human Health Sciences
4770 Buford Highway
Chamblee, GA 30341-3717
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO
ATSDR can also tell you the location of occupational and environmental health clinics. These clinics specialize in recognizing, evaluating, and treating illnesses resulting from exposure to hazardous substances.